Science and technology

Difference Engine

The dirty secrets of clean cars

WHEREVER automotive engineers gather, some wag will sooner or later announce that hydrogen is the fuel of the future—and always will be. The hydrogen-powered car has been just around the corner for decades. However, judging from announcements by Honda, Hyundai and Toyota at last week’s motor shows in Los Angeles and Tokyo, hydrogen cars will be hitting the showrooms from spring 2014 onwards. It seems the future is about to arrive.

Hydrogen’s attraction as a transport fuel is that, unlike petrol, diesel, kerosene, natural gas and every other hydrocarbon fuel, it contains, well, no carbon. Burning it therefore creates no carbon-based greenhouse gases—at least, not in the engine. However, if air is used as the oxidiser instead of pure oxygen, burning hydrogen produces all the noxious oxides of nitrogen that fossil fuels generate. These are an even bigger curse than carbon dioxide as far as damaging greenhouse gases are concerned.

That is why work on using hydrogen as a fuel for a modified internal-combustion engine has been more or less abandoned, even though getting such a power unit into production was considered cheaper than any of the clean alternatives. BMW built a couple of hydrogen-powered supercars, only to find them no cleaner than clunkers from the days before catalytic converters.

Hence the embrace of fuel cells, which extract chemical energy from hydrogen without resorting to combustion. The process is essentially the opposite of electrolysis: instead of using electricity to split water into hydrogen and oxygen, a fuel cell combines the two gases electrochemically to produce water, while generating an electric current in the process. A fuel cell’s only emissions are thus water vapour and heat.

At its simplest, the “PEM” (short for proton-exchange membrane) type of fuel cell used in cars has two electrodes—an anode and a cathode—separated by an electrolyte in the form of a polymer membrane coated with a platinum-palladium catalyst. Hydrogen from a fuel tank is pumped into the anode side of the cell, while the cathode is surrounded by oxygen drawn from the air.

As the hydrogen seeks to migrate from the anode to the cathode, the catalyst strips electrons from it, allowing only hydrogen ions (protons) to pass through and migrate to the cathode, where they combine with the oxygen to form water. The electrons rejected by the membrane are diverted via an external circuit to perform useful work (drive a motor, power a heater, light a bulb, etc) before reaching the cathode to complete the circuit. As a PEM cell can deliver a little under one volt, many of them have to be stacked together like a sliced loaf to produce a useful voltage.

Fuel-cell stacks are potentially three or four times more efficient than internal combustion engines. More to the point, cars using them are essentially electric vehicles, but without the heavy battery. As such, they solve two big problems that plague battery-powered electric vehicles: their limited range and their long recharging time. Vehicles powered by the latest fuel-cell stacks can achieve over 300 miles (480km) on a tankful of hydrogen. Filling the tank takes five minutes at most. And, like battery electrics, they are classed as zero-emission vehicles (ZEVs).

This matters because carmakers have to show state authorities (California’s Air Resources Board, in particular) that they are working hard to meet those states' zero-emission sales targets. They have grown despondent about battery-powered electric cars—with their paltry ranges and long recharging times—being able to do the job, even if the batteries were to halve in price or double in range.

By contrast, hydrogen vehicles—which behave more like conventional cars—could help them get closer to the mandated requirements. By 2025, car companies will need to have sold at least 1.5m zero-emission vehicles in California under the latest clean-air rules. In a normal year, Californians buy around 1.7m new cars. That means something like 15% of all new cars sold in the state will have to be ZEVs by 2025.

Seven other states, including New York, Connecticut and Massachusetts, have now adopted similar rules. Between them, the eight states in question account for one out of four new cars bought in America.

Another attraction is the rate at which fuel-cell costs are declining. Despite the billions of dollars thrown at lithium-ion technology—the battery of choice for plug-in electrics—progress seems to have stalled, while costs have remained stubbornly high at around $2,000 per kilowatt of power. The contrast with fuel cells could not be greater. When unveiled to the public in 2007, the 100-kilowatt stack in the Honda Clarity hydrogen car was reckoned to have cost the company $350,000 per unit—ie, $3,500 per kilowatt. No wonder Honda built only 200 Clarity test cars for public trials.

Over the past six years, however, manufacturers have more than halved the cost of their experimental stacks. Today, they cost less than $1,500 per kilowatt to make in short runs (see “End of the electric car”, October 15th 2012). If they were mass-produced in tens of thousands instead of by the handful, the Department of Energy believes they could be manufactured for less than $50 per kilowatt—much the same as a typical internal combustion engine.

The other obstacle to the wide deployment of PEMs—the expense of their catalysts—could be dealt with if a cheap catalyst could be found that worked as well as platinum-palladium, and did not get so easily poisoned by impurities (such as carbon monoxide) in the hydrogen fuel. Some progress has been made with iron-based catalysts, but their activity is still too low to be practical. Alternatively, if the expensive platinum-palladium catalyst could itself be made more catalytically active, then less would be needed to do the job, and fuel cells would inch closer to becoming commercially viable. Given the amount of research underway, both approaches are likely to yield results before the decade is out.

All this may not, however, be enough to drag that much-vaunted future into the present. First, there is the problem of providing the hydrogen fuel, along with the infrastructure for transporting it to garages across the country. Of the 100 or so hydrogen-filling stations dotted around America, fewer than a dozen are open to the public. The rest are reserved by industry, the armed services, government agencies and research institutions for their own private use.

California's state government has approved plans to spend $20m a year over the coming decade to build more than 100 hydrogen stations for public use. By one estimate, covering the rest of the country with the barest network of such stations would cost $20 billion. Another study suggests making hydrogen dispensers as common as petrol pumps would cost America the small sum of half a trillion dollars.

Then there is the question of where the hydrogen comes from. At present, industrial hydrogen (which is used as a feedstock for refining oil, as well as for making chemicals, electronics and foodstuffs) is produced by reforming natural gas with steam. This is not a particularly clean process. According to the National Renewable Energy Laboratory, a federal facility in Colorado, producing a kilogram of hydrogen by steam reformation generates 11.9 kilograms of carbon dioxide. As the Honda Clarity could travel 68 miles (109km) on a kilogram of hydrogen, it would cause 175 grams of carbon dioxide to be dumped into the atmosphere for every mile it was driven.

By way of comparison, Volkswagen’s small diesel cars produce 145 grams per mile. On that reckoning, even petrol-electric hybrids like the Toyota Prius, which produces 167 grams per mile, are cleaner than the fuel-celled Clarity. Admittedly, fossil fuels also produce carbon emissions while being dug out of the ground, refined and transported to the pump. But burning hydrocarbons in internal-combustion engines is becoming cleaner all the time. When measured on a well-to-wheels basis, the steadily declining emission levels of conventional vehicles is putting the squeeze on so-called ZEVs.

If the zero-emission rules of California and elsewhere are to mean anything, then the hydrogen has to be made by clean and costly electrolysis of water rather than by cheap and dirty steam reformation of natural gas. And the electricity used to separate water into hydrogen and oxygen has itself to produce no greenhouse gases while being generated. The only way to do that is to rely strictly on renewables like wind and solar energy, or carbon-free hydroelectricity and nuclear power.

Unfortunately, renewables do not scale particularly well. Meanwhile, precious few hydroelectric sites are left to be exploited. And nuclear power is, at best, a long-term option these days.

Lacking clean electricity, the plug-in electric vehicles and hydrogen cars that manufacturers are being pressed to produce to meet the ZEV goals could wind up being bigger polluters than the petrol and diesel vehicles they replace. That is the message carmakers hope will be heard loud and clear by lawmakers everywhere, for, as they are likely to lose money on every ZEV they sell, they are hoping the authorities will relax the rules once the goals are seen to be unachievable—at least, at prices motorists can afford. Such accommodations have been made several times before. If they are made again, the future of the hydrogen car will stay where it has always been: in the future.

Let us say you are a car nerd with a fetish for the newest hottest fads.

And you had a petrol luxury SUV.
And you buy a diesel for better cruise miles on the highway on long trips.
And an all electric battery car for in-city, ultrashort errands.
And natural gas is the new thing, so you get one of those too.
And now the car hipster are pushing the hydrogen vehicles. Water is your exhaust!

So your garage is full and nothing is compatible.
Your batteries are short charging.
The natural gas fill up station went bankrupt from lack of customers.
The Hydrogen vendor is in the Midlands and you live on the coast.
And nothing seems long term but you still love the throaty exhaust of a V8.

---

Your neighbor has had the same beater compact Toyota Corolla for 20 years while you have experimented with your 'green' whims.

---

The green car is one you use for 20 year--even if it uses old fashioned petroleum.
Building a car takes energy, work, engineering and resources.
And building 5 cars takes far more energy than building one car.
And many inspired green cars are technological dead ends.
They are not sustainable technology.
---
And everything is in flux.
Many new fads will go extinct.
Many of these will not prove to be Green Cars but White Elephants.
---
Buy one car, keep it maintained, drive it to the ground.
Frugality is Green.

Part of my MSc study led to comparative study of different modes of trasport on energy efficiency and safety.
Private motor car came almost to the bottom of almost every table from life safety (No. of death per passenger km: Bottom), energy efficiency (primary energy used per passenger km: Second bottom after airliners), and to space efficiency (No. of passengers that can travel per 1m width of the right-of-way: Bottom)
So, in terms of efficiency and safety between different modes of transportation, clean cars are equivalent to polished turd.

People claim that the problem is that we need to reduce the amount of man-made carbon dioxide because it causes dangerous global warming. But the evidence is against them.

The world has not warmed for the last 17 years so proving that the climate models are worthless and the most recent scientific (not the summary for policymakers) study by the IPCC shows that their confidence levels on the amount of heating caused by carbon dioxide, their ability to model clouds and in their dire predictions have all reduced since the last study.

The world has vast amounts of fossil fuel resources available and the evidence is that the moderate increase in carbon dioxide levels has resulted in a substantial increase in the productivity of plants and made a major contribution to reducing starvation and the cost of food. One study estimates the benefits as USD3.5 trillion.

Looking for the ecologically best 1-person motorized vehicle has given us the motorcycle. A 175cc motorcycle can be produced that is cleaner than any automobile. The obvious problem is that far more people want to ride to work in the rain in a mid-sized automobile than on a 175cc bike. I must admit that since there is 6 cm of snow on the ground outside, I am among those who would not choose a motorcycle.

Sadly, I have sold my bike. Today I ride the bus. Where I live, public transit is rapid and convenient.

You have all the data on your side. On the other hand, as a biker for 20+ years, I can tell you that
the single person in a mid-sized (inefficient) car believes the roads were made for him.

The battle we need to fight is not one of science. That war is over, and we won.

It's one of status. Too many people think "I'm better than you because I drive my car and you walk/ride a bus/take the tube."

I can think of but one way to change their minds. Pauperize them. Make their behaviour so costly they cannot continue it, regardless of income or assets.

And that, given that they are in the overwhelming majority, is going to be hard to do.

Look, we've been dealing with you folks for over a century, ever since Arrhenius started working with CO2.

Take a transparent container of CO2 and a transparent container of air. Shine a heat lamp on one side of each container. See which container you can feel the heat coming from on the other side. I'll give you a hint, it isn't the one with CO2.

Now imagine we are making millions of these containers and placing them in the atmosphere. When the infrared from the Earth tries to escape, it is meeting this CO2 and getting stuck. Pretty easy concept.

How does heat transfer between liquids and gases? That's elementary, and you can read a first year physics book on that. The actual details, such as why the ocean and atmosphere temperatures aren't always identical, of course are somewhat more complicated, but not too difficult. Finally, introductory statistical mechanics can explain the energy balance. There's no excuse to be ignorant and pontificating, go read!

We know changes in incident radiation are not sufficient to explain what's going on here on Earth. But then what else is the Sun going to do to affect climate? What, solar flares? Corona effects? These are absolutely tiny compared to every-day radiation.

I do not deny that the climate changes. You, against all the evidence, deny that it changes naturally.
To paraphrase "the climate has changed naturally naturally before, but this time, I have decided that it is man-made."
How did all this heat get into the ocean without the atmosphere getting any warmer? And, in particular, how did it get into the deep water. And finally, how accurately has it been measured, and how good is the science behind the measurements?
The IPCC has failed to look at the sun apart from direct solar heating. There are many other effects that can affect the world's climate but the IPCC has failed to investigate them.

Help me. A battery stores energy and a motor uses this energy to produce power. The more power the motor produces, the greater the car's acceleration.
How then can you measure the cost of a battery as $2,000 per kilowatt? Surely you need to use units of energy, like kilowatt-hours? If so, how can you compare the cost of storing a unit of energy to the cost of generating a unit of power?

Everyone agrees that, in an ideal system, (which the world is not) doubling of carbon dioxide would cause a warming of about 1°C.

The IPCC invoked a "climate forcing factor" based on the hypothesis that the increased warming will produce more water vapour – the main greenhouse gas – and this in turn will produce more warming. When fed into a climate model this positive feedback factor increased warming from 1° to 3°. the latest scientific report from the IPCC has reduced the 3° to about 2°. But, as many climate modellers happily admit, the climate models do not manage cloud effects in any realistic way. If, as a result of the increased water vapour, cloud cover increased by 1%, the global warming would effectively disappear.

If the strong positive feedback factor really existed, the world would have frozen or fried millions of years ago. The fact that it has not done so should indicate to anyone who thinks about it that the climate system has built in stabilising factors that prevent runaway warming.

I absolutely agree with @Connect The Dots. The cradle-to-grave impact (including but not limited to AGW) of generating a new car is far worse than that of the extra fuel burned by an older car that is kept in good condition and used for decades.

However, we can't all drive the 1998 Toyota Corolla for the rest of time and so we need our early adopters to help us point our technological development in the right direction (i.e. toward more sustainable fuel choices and away from that gas guzzling SUV).

All the current options have their problems (Hydrogen with its production cycle, electric with its limited range, connection to coal-fired energy, and use of toxic rare-earth metals) and I haven't seen that breakthrough vehicle out there yet that will sweep all the ICE cars off the road in one big push like the model T did with the horse and buggy.

Nevertheless, it's not like the model T happened overnight and the next day there was an Exxon station around the street to fill up the tank. Cars happened over years of innovation and perfection with (dare I say it?) millions of dollars of government subsidy - both direct and indirect - through development of infrastructure, tax subsidies for oil exploration and refinement, trade deals favorable to auto manufacturers ... the list goes on and on.

If we wait around for the perfect automobile to happen in someone's basement, or through the generosity of a few venture capitalists, it will be too late. Unless we as a society - and that includes the public and private sectors - start to take the very real costs of AGW into account when we consider the costs of energy production and take steps to mitigate those disastrous impacts, we will not be able to avoid them and will drive our nice, cheap, gas-powered automobiles right off the cliff of history.

And if you think I'm just some tree-hugger when I talk about the costs of AGW, then go to the boards of directors of any large insurance company and ask them why they are adding these costs to their long-term risk assessments.

Li-Ion batteries can cost as low as $100/kW today, and nowhere near $2000/kW claimed in the article. The battery of the roughly 300-mile-range Tesla Model S P85, in production for over a year, delivers 320kW of power and costs around $30k (or perhaps only $25k http://insideevs.com/tesla-battery-in-the-model-s-costs-less-than-a-quar...), hence $30k/320kW is about $100/kW. Batteries' leap to $50/kW seems far more plausible than that of a $1500/kW Hydrogen fuel cell.

and will cover the entire 48 contiguous US states by 2015 and will ultimately pay for itself using solar. Plans for such coverage with Hydrogen stations does not exist, perhaps because of the billions in costs cited here.

There is always something left behind in the analysis of emissions: where the gases are produced. A stationery power station technically can achieve better energy efficiency and better filtering of gases than a combustion engine installed in a car. Furthermore, power plants that use renewable fuels, such as ethanol, can be placed in farms, where the carbon gases can be better “eaten” by the vegetables. Car companies and urban sites made us insensible to smell car gases, but this doesn’t mean that we are not smoking them in urban areas. Thus, there is another positive spin off from electric cars that is to get gases apart from cities and human beings. Research has proved that the reduction of emissions in cities like Sao Paulo have reduced pulmonary illnesses cases in the Sao Paulo University hospital (USP). A clever and correct evaluation of the benefits of electric cars should put this all together, otherwise, they may be considered just as campaigns in favor of the century old combustion engine.

Manufacturers also have to crack the storage problem. Existing technology requires heavy vessels to hold pressurized h2 gas or active cryogenic systems to keep it cold enough to stay liquid. Neither is particularly safe in a moving vehicle. Future technology may bring material storage, where h2 is stored within other materials, but that is over a decade away.

The problem with Occam's razor is that it applies best to philosophy, not necessarily to science. Would Occam have chosen Newtonian gravity or general relativity?

Yes, there are plenty of examples of scientific consensus altering course to accept what it once considered wrong, or even ludicrous - but you defeat your own argument when you give these examples of "discoveries" that you would have never heard of except that the consensus changed to accept them!

You show me one person with a crazy theory that turned out to be an unappreciated genius and I'll show you 1,000 scientists who turned out to just be flat wrong.

Consensus doesn't make you right - but being against the consensus doesn't make you right, either - and especially in a field in which I'm no expert (despite being a researcher in atmospheric science) I'm more inclined to trust the consensus of a few thousand highly trained colleagues - especially when there's no competing theory that even comes close to explaining the data.

You say the models aren't accurate enough because they've missed a few years of data points? I say the current temperatures are well within the range of uncertainty from the model results I've seen and until you show me a model based on no AGW that fits the data better, I'm going with the consensus.

Oh, and I've read many climate science papers - especially those based on modelling - that provide everything one needs to reproduce their results. I've also read plenty of papers in other fields from pharmaceuticals to optics to biology to game theory that did not. Climate science is not some shady outlier in this respect. Try again.

Honestly, I've never been enthusiastic about a "hydrogen economy." Now that we have adsorptive storage solutions for fueling the hydrogen car concept can at least shed the millstone of having to lug around a giant pressure vessel for carrying a decent supply of the lowest density gas. However, I have yet to see a good response to the following question: why bother burning natural gas-derived hydrogen, with all of its attendant technical difficulties, lack of infrastructure, and the inevitable less-than-perfect efficiency of reforming, when you can just utilize a lot of pre-existing infrastructure and burn the natural gas directly?

The answer in this case appears to be the initiatives for ZEVs pushing emissions to an earlier stage of the process for appearance's sake - in other words, a cosmetic evasion of the spirit (though not the letter) of a well-intentioned law. The road to hell, etc., etc.

First, I have been accepted as an expert reviewer for this IPCC report in the energy field. Several of the comments I made were accepted. But that does not mean that I agree with the main thrust of the IPCC and the same goes for many of my friends who have also been accepted as expert reviewers. Yet the IPCC claims that all of us I agree with their main theme. It is far from the truth. The truth is that there is quite a small number of very influential scientists who are wedded to the dangerous global warming myth.

And where did your "tens of thousands" come from? And what if they did exist anyway? Science is not determined by consensus, science is determined by the evidence. Galileo – and many many others – were lone voices against the consensus and were right.

The evidence is that the world has not warmed for the last 17 years against all the predictions of climate models. If the models cannot accurately predict what will happen, they are worthless.

Many reputable scientists believe that we are in for a cooling period driven by solar effects. This is not something that the IPCC has studied in any depth. Yet the whole world relies on the heat from the sun.

For the foreseeable future LNG from the cheap shale gas is the way to go for America. Might be possible to build fuel cells that take methane.

Long term using overcapacity from renewables to produce fuel cell feedstock is certainly an option. Currently, this is only attractive where LNG is taxed significantly more favourably than other fuels.

Scalability has little to do with either of these: converting renewable energy into feedstock can replace batteries on site or be fed into existing pipelines depending on what's needed.

You're seriously suggested a centralized production model for hydrogen? Either you're unaware of the massive technical problems inherent in long-range distribution of hydrogen, or you are encouraging hydrogen from electrolysis now (rather than in the future). Neither of these are viable from an efficiency perspective; the only real option for efficient distribution of hydrogen in the near term is modular SMR installations at filling stations, which of course goes against your entire point about localized emissions and distribution. I doubt that multiple large urban points sources of NOx will produce any better health effects than several thousand small mobile sources.

I'm also unsure about fuel cell vehicular operating life in comparison to an internal combustion engine. If you focus on the engine-generator system vs the IC system, then sure, but I would be much more concerned about the adsorption system that the hydrogen vehicle depends on. The picture doesn't look so clear if the packing in the fuel tank is slowly poisoned by feed impurities, and let's face it, people are very good at doing bad things for their vehicles in that way.

In fact, I think that the point you claim the article is mistaken about - that of the lack of filling stations - is far and away the most salient point against hydrogen vehicles. The infrastructure for natural gas distribution and extraction is in place; the only thing missing are the pumps and storage tanks. The infrastructure for hydrogen has yet to be built, and what's missing there is a huge amount of generation capacity as well as the filling stations and distribution systems. One of these is much less expensive than the other.

The use of the kilowatt is correct. The article compared the power that could be delivered to the wheels, not the energy that can be stored by the vehicle.

Fuel cells and petrol engines cannot store energy. However better fuel cells can transform hydrogen more quickly and power a bigger electric motor that can turn the wheels faster. Battery performance is measured not just by storage, but how quickly the stored energy can be released, which was the metric in this comparison. Similarly, better petrol engines transform gasoline into energy more quickly, making the wheels spin faster.